JP3296208B2 - Curve curvature estimator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curve curvature estimating apparatus, and more particularly, to the influence of the center of gravity slip angle in calculating the curve curvature when the vehicle center of gravity slip angle becomes large, such as when the vehicle is running at a low vehicle speed or turning a large curvature. The present invention relates to an apparatus for estimating a curvature of a curve, which is suitable for use in reducing the curvature.

[0002]

2. Description of the Related Art In recent years, various technologies for assisting a driver, such as a navigator system, have been developed for automobiles, and further, technology development relating to automatic driving for automatically performing a driving operation on behalf of a driver. Is being promoted. The driving operation by the driver controls the vehicle speed and performs steering according to the grasped road conditions and driving conditions while grasping the road conditions and the driving conditions of the vehicle. Various functions need to be computerized or mechanized.

For example, in order to automate the steering of a vehicle, a mechanical function of performing a steering operation on behalf of a driver (ie, a mechanical function)
Needless to say, a steering actuator is required, but various functions for controlling the operation of the steering actuator are required. That is, as described above, it is necessary to have a function of grasping the road condition on which the vehicle travels, that is, the curve condition of the front traveling road, and the traveling condition of the vehicle, that is, the relative position and the vehicle speed of the vehicle with respect to the traveling road. Further, it is necessary to have a function of setting a target steering angle in accordance with the grasped road conditions and running conditions of the vehicle, and controlling the operation of the steering actuator based on the target steering angle.

[0004] In particular, in order to grasp the curve situation of the road ahead, as shown in FIG. 4, for example, a television camera (generally a CCD camera) for photographing the road ahead of the vehicle 1 as shown in FIG.
2, a guide line such as a white line on the road is recognized from the image information captured by the TV camera 2, and a curve curvature (or radius) of the road is determined from the recognized guide line. ing.

In this case, as shown in FIG. 5, since the original image taken by the television camera 2 is a perspective image, the original image is temporarily converted into a planar view (top view) image, and then guide lines are matched by circles, for example. Or geometrically calculated from the angle between the vehicle direction or the like and the tangent to the guide line to determine the curve curvature. For example, Japanese Patent Publication No. 63-314616 discloses a technique of selecting two points of a guide line in front of a vehicle recognized from a converted plane image, and obtaining a tangent to each of the guide lines at these two points. There is disclosed a technique for detecting the curvature of a guide line based on the angle between these tangents and the vehicle traveling direction.

In such a method, for example, as shown in FIG. 6, on a curved road, a travel path 7 (particularly a target travel line such as a travel path center line) 7 at a point P1 ahead of the vehicle 1 by a predetermined distance L. Direction, that is, the tangential direction A2 of the traveling path
The angle θ between the vehicle and the direction A1 in front of the vehicle is determined, and the curvature ρ (= 1 / R) of the curved road is determined from the following equation (1).

1 / R = ρ = sin θ / L (1) This is the turning center angle θc when the vehicle travels on a curved road from the current vehicle point to a traveling road point by a distance L from the current vehicle point. Equally, when the turning center angle θc is minute, the following equation (2) is established. sin θc ≒ L / R (2) Here, if θc = θ, the following equation (3) holds, and the equation (1) can be derived.

Sin θ ≒ L / R (3) In addition, since the brightness of the guide line is generally higher than that of a normal road surface, for example, a road image is searched for brightness in the scanning line direction and the brightness is determined. The high portion is set as a guide line candidate point, and the guide line can be recognized from the guide line recognition information and the guide line candidate point information obtained immediately before.

For example, Japanese Patent Application Laid-Open No. 7-85249 discloses that
A brightness change is searched in the horizontal direction in the white line search area based on the image information, and a portion where the brightness change is extremely small is determined to be a road portion, and a brightness change adjacent to the road portion where the brightness change is extremely small is determined. A technique for recognizing a large portion as a white line is disclosed.

[0010]

By the way, when the curve curvature is calculated geometrically from the angle between the vehicle direction and the like and the tangent of the guide line to obtain the curve curvature, as shown in FIG. That is, it is assumed that the vehicle center line direction A1 is always tangential to the curved road (target traveling line) 7.

However, since the center of gravity slip angle β _G is generated in the turning vehicle, the center line direction A 1 of the turning vehicle is not always directed tangential to the target traveling line 7. . That is, as shown in FIG. 7, when the vehicle speed is in a middle speed range (for example, about 40 km / h), the center line direction A1 of the vehicle at the time of turning is substantially tangential to the target traveling line 7 (see the vehicle 101). ), If the vehicle speed is in a low speed region (for example, a region where the vehicle speed is lower than about 40 km / h), a center-of-gravity slip angle β _G occurs, and the center line direction A1 of the vehicle at the time of turning is outside the tangent direction to the target traveling line 7. (See the vehicle 102), and if the vehicle speed is in a high-speed region (for example, a region where the speed is higher than about 40 km / h), a center-of-gravity slip angle β _G is generated and the center line direction A1 of the vehicle at the time of turning becomes There is a characteristic that it faces inward from the tangent direction to the target traveling line 7 (see the vehicle 103).

When the center line direction A1 is different from the tangent direction to the target travel line 7, the center line direction A1 of the travel road ahead by the distance L calculated based on the image captured from the camera 2 installed in this vehicle is calculated. The inclination, that is, the angle θ formed between the tangential direction A2 of the traveling road and the direction A1 ahead of the vehicle is not equal to the turning center angle θc when the vehicle has traveled a curved road up to the traveling road point by a distance L.

Therefore, a large error may occur in the curve curvature ρ calculated based on the angle θ. In particular, when the vehicle is traveling at a low speed or on a curved road having a large curve curvature (that is, a small curve radius), the estimation error of the curve curvature ρ due to the center-of-gravity slip angle β _G increases.

The present invention has been made in view of the above-described problems, and has as its object to provide a curve curvature estimating apparatus capable of accurately estimating a curve curvature in consideration of a center-of-gravity slip angle.

[0015]

According to a first aspect of the present invention, there is provided a curve curvature estimating apparatus which is mounted on a vehicle and captures an image of a traveling road ahead of the vehicle, and converts the image into a plane. Image conversion means for converting into a visual image, and an angle θ between the direction of the traveling road ahead of the reference point of the vehicle by a predetermined distance L from the reference point of the vehicle and the vehicle body direction based on image information from the image conversion means, In a curve curvature estimating device provided with a curvature calculating means for calculating a curve curvature of the traveling road from the angle θ and the distance L, the value of the angle θ or the distance L is used to calculate the curve curvature. The present invention is characterized in that a center-of-gravity slip angle correction means for correcting the center-of-gravity slip angle is provided in accordance with the center-of-gravity slip angle generated at the time of turning.

According to a second aspect of the present invention, there is provided the curve curvature estimating apparatus according to the first aspect, wherein the reference point of the vehicle is the center of gravity of the vehicle body, and the means for correcting the center of gravity slip angle corresponds to the vehicle. The value of the distance L is corrected by the distance Lβ between the intersection of the perpendicular line drawn from the center of the turning radius to the vehicle body center line and the vehicle body center line and the center of gravity.

According to a third aspect of the present invention, there is provided a curve curvature estimating apparatus according to the second aspect, wherein the center-of-gravity slip angle correction means determines the distance Lβ between the intersection and the center of gravity used for the correction. From the vehicle speed V of the vehicle, the distance lr from the center of weight of the vehicle to the rear wheel axle, and the constant b, the equation Lβ = lr (1-
bV ² ), the rearward direction of the vehicle body is calculated as positive from the center point of the vehicle weight, and the correction is performed by adding the distance Lβ between the intersection and the center of gravity to the distance L. Is calculated from the angle θ, the distance L, and the distance Lβ between the intersection and the center of gravity using the equation ρ = sin
It is characterized in that it is configured to be determined by θ / L + Lβ.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 3 show a curve curvature estimating apparatus as an embodiment of the present invention.
As shown in FIG. 1, the curve curvature estimating apparatus includes a CCD camera (imaging means) 2 and an image processing apparatus (image converting means).
2A and a curvature calculation means 30, and the curvature calculation means 30 is provided with a gravity center slip angle correction means 31 for correcting according to a gravity center slip angle generated when the vehicle turns.

The CCD camera 2 is a television camera 2 (see FIG. 4) fixed to the vehicle 1, and obtains a perspective image by capturing an image of a running path ahead of the vehicle 1. Also, the image processing device 2
A converts a perspective image captured by the CCD camera 2 into a two-dimensional image. Then, the curvature calculation means 30 travels on a travel path (travel target line) at a point P1 ahead of the reference point (center of gravity) of the vehicle 1 by a predetermined distance (forward fixation distance) L set according to the traveling state of the vehicle. Angle θ between the direction of the road (tangential direction of the traveling road) and the direction of the vehicle (front of the vehicle center)
(Angle detection unit) 32, and a calculation unit 33 that calculates the curve curvature ρ of the traveling path (traveling target line) from the angle θ and the distance (forward gaze distance) L.

The angle detector 32 converts the original image captured by the television camera 2 into a two-dimensional image (see FIG. 5).
By recognizing a guide line such as a white line based on the above, the angle θ can be geometrically obtained. In addition, the recognition of the guide line is performed by a known technique (for example, Japanese Patent Laid-Open No. 7-85249).
Can be performed. Further, in the calculation unit 33,
A curve curvature is calculated from the distance L and the angle θ corrected by the center-of-gravity slip angle correction means 31 provided in the curvature calculation means 30.

Here, the gravity center slip angle correction means 31
According to the correction means 31, the vehicle speed V detected by the vehicle speed sensor 41, the distance lr from the vehicle center of gravity to the rear wheel axle, and the constant b are calculated from the vehicle center of gravity CG by the following equation (4). The distance between the intersection point and the center of gravity with the vehicle body rearward direction being positive (the distance between the intersection point P of the vehicle body center line CL with the perpendicular drawn from the center O of the turning radius of the vehicle to the vehicle body center line CL and the center of gravity CG) Lβ (Distance Lβ calculation unit) 31A.

Lβ = lr (1−bV ² ) (4) The distance lr and the constant b are stored in advance. Further, the correction means 31 adds the distance (the center-of-gravity slip angle-corresponding distance or the turning center correction distance) Lβ calculated by the distance Lβ calculation unit 31A to a predetermined distance (front fixation distance) L (L + Lβ). Thus, a function (distance L correction unit) 31B for correcting the distance L is provided.

Here, the principle of correcting the distance (forward fixation distance) L will be described. FIG. 2 shows a low vehicle speed (for example, 40 km /
h) and traveling on a curve having a relatively large curvature. As shown in FIG. 2, at a low vehicle speed, the vehicle 1 moves as shown by the vehicle body center line CL,
The vehicle turns in the vehicle body direction (direction in front of the vehicle body) in a direction inclined to the outside of the curve with respect to the traveling direction of the vehicle (see the vector direction of the speed V). The angle β _G between the traveling direction V of the vehicle and the direction of the vehicle body (refer to the center line CL) is called a center-of-gravity slip angle.

For this reason, based on the information from the camera 2 fixed to the vehicle body of the vehicle 1, the angle detector 32 detects the traveling path direction (tangential direction of the traveling path) and the vehicle direction ( In the case shown in FIG. 2, the angle θ is larger than the center angle θc required for the vehicle 1 to move forward on the curve by the distance L than the center-of-gravity slip angle β. _One larger by _G (θ = θc +
β _G ), and the correct curvature ρ cannot be estimated.

Therefore, the vehicle 1 sets the curve at the central angle θ = (θ
c + β _G ) ahead of the vehicle body (center line C)
Considering the moving component L ′ to the L), the curvature ρ may be calculated from the distance L ′ and the angle θ. Distance L '
Is, as shown in FIG. 2, from the turning center 0 to the vehicle center line CL.
From the intersection P2 of the vertical line lowered to the vehicle body center line CL and the angle detection point P1 in front of the center of gravity CG of the vehicle 1 by a distance L.
L '= L + Lβ, where the distance from the intersection P2 to the center of gravity CG of the vehicle 1 is the turning center correction distance Lβ.

As described above, the turning center correction distance Lβ can be approximated by the vehicle speed V, the distance lr from the center of gravity of the vehicle weight to the rear wheel axle, and the constant b as shown in equation (4) from the equation of motion of the vehicle. , L ′. In addition,
At a high vehicle speed (for example, at a speed higher than about 40 km / h), the vehicle body center of the vehicle 1 turns in a posture inclined more inward of the curve than the traveling direction of the vehicle, contrary to the one shown in FIG. Is the central angle θ at which the vehicle turns.
c is smaller than the center-of-gravity slip angle β _G (ie,
θ = θc−β _G ). In this case, since the intersection P2 is located in front of the center of gravity CG of the vehicle 1, the turning center correction distance Lβ
Is a negative value, and the distance L 'is smaller than the distance L.

The arithmetic unit 33 calculates the distance (= L) corrected by the center-of-gravity slip angle correction means 31.
+ Lβ) and the angle θ from the following equation (5) to obtain the curve curvature ρ
Is calculated. ρ = sin θ / (L + Lβ) (5) Since the curve curvature estimating apparatus as one embodiment of the present invention is configured as described above, data corrected in accordance with the center-of-gravity slip angle is obtained. (Here, since the curve curvature ρ is calculated based on the corrected distance L ′ = L + Lβ), there is an advantage that the curve curvature can be accurately estimated even if the center of gravity slip angle occurs.

Therefore, various vehicle controls using the curve curvature can be performed with higher accuracy. In particular, since an error in estimating a curve curvature, which is particularly problematic when traveling on a large curvature curve at a low vehicle speed, is reduced, it is possible to accurately perform various vehicle controls at a low vehicle speed based on the curve curvature estimation. Become like

For example, FIG. 3 is a diagram showing the effect of the present device. When the vehicle enters a sharp curve having a radius of 25 m at a vehicle speed of 25 km / h, automatic steering is performed based on the curve curvature obtained by the curve curvature estimating device. It is a simulation result. (A) is the lateral displacement of the center of gravity, (B) is the steering wheel angle,
(C) shows the lateral acceleration and (D) shows the lateral jerk. The solid line shows the case with Lβ correction and the broken line shows the case without Lβ correction. As shown in the figure, it can be seen that the lateral displacement amount of the center of gravity is appropriately corrected in the automatic steering that has performed the Lβ correction.

In the present embodiment, although not particularly limited, the correction corresponding to the center-of-gravity slip angle is performed only when the vehicle speed is low (for example, when the vehicle speed is 40 km / h or less). You may. This makes it possible to reduce the influence of the center-of-gravity slip angle under conditions where the influence of the center-of-gravity slip angle is greatest (at low vehicle speed) while simplifying the control logic, and a certain effect can be obtained.

In this embodiment, the angle θ based on the image captured by the camera is not corrected, and the distance L in the vehicle body direction to the angle detection point P1 is set to L ′ so as to correspond to the angle θ. Although the correction is made, the angle θ itself may be corrected by the gravity center slip angle β _G and the distance L may be used as it is.

[0032]

As described above in detail, according to the curve curvature estimating apparatus of the present invention, in the curve curvature estimating apparatus, when calculating the curve curvature, the value of the angle θ or the distance L is used for the vehicle. Since the correction is made according to the center-of-gravity slip angle generated at the time of turning, there is an advantage that even when the center-of-gravity slip angle occurs, the curve curvature can be accurately estimated.

According to the curve curvature estimating device of the present invention, the correction according to the center-of-gravity slip angle can be reliably performed, and the accuracy of curve curvature estimation can be easily improved. According to the curve curvature estimating device of the present invention, the correction according to the center-of-gravity slip angle can be easily and reliably performed from the easily detectable information,
The accuracy of estimating the curve curvature can be easily and reliably improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a curve curvature estimating apparatus as one embodiment of the present invention.

FIG. 2 is a diagram illustrating a gravity center slip angle corresponding correction in a curve curvature estimating apparatus as one embodiment of the present invention.

FIGS. 3A and 3B are time charts (calculation examples) showing an improvement in estimation accuracy by the curve curvature estimating apparatus as one embodiment of the present invention, where (A) is a lateral displacement of the center of gravity, (B) is a steering wheel angle, and (C). Represents lateral acceleration, and (D) relates to lateral jerk.

FIG. 4 is a schematic side view of a vehicle illustrating a conventional curve curvature estimating device.

FIG. 5 is a diagram illustrating a conventional curve curvature estimating device.

FIG. 6 is a diagram illustrating a curvature estimation method of a conventional curve curvature estimation device.

FIG. 7 is a diagram illustrating a problem of a conventional curve curvature estimating device.

[Explanation of symbols]

 Reference Signs List 2 CCD camera (imaging means) 2A Image processing device (image conversion means) 30 Curvature calculation means 31 Center of gravity slip angle corresponding correction means 32 Angle detection unit 33 Calculation unit 41 Vehicle speed sensor 31A Distance Lβ calculation unit 31B Distance L correction unit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-191431 (JP, A) JP-A-6-229267 (JP, A) JP-A-7-81603 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G08G 1/09-1/16 B60R 21/00

Claims (3)

(57) [Claims] 1. An image pickup device mounted on a vehicle for taking an image of a traveling road ahead of the vehicle, an image conversion device for converting the image into a two-dimensional image, and an image information from the image conversion device. A curvature calculating means for determining an angle θ between the direction of the traveling road ahead of the reference point of the vehicle by a predetermined distance L and the vehicle body direction, and calculating a curve curvature of the traveling road from the angle θ and the distance L; A center-of-gravity slip angle correction means for correcting the value of the angle θ or the distance L in calculating the curve curvature according to a center-of-gravity slip angle generated when the vehicle turns. A curve curvature estimating device. 2. The vehicle according to claim 1, wherein the reference point of the vehicle is a center of gravity of the vehicle body, and the center-of-gravity slip angle corresponding correction means includes a perpendicular line lowered from the center of the turning radius of the vehicle to the vehicle body center line and the vehicle center. 2. The curve curvature estimating device according to claim 1, wherein the value of the distance L is corrected based on a distance Lβ between the intersection of the line and the center of gravity. 3. The center-of-gravity slip angle correction means calculates the distance Lβ between the intersection and the center of gravity used for the correction by the vehicle speed V, the distance lr from the center of gravity of the vehicle weight to the rear wheel axle,
From the constant b, by the formula Lβ = 1r (1−bV ² ),
The vehicle body rearward direction is calculated as positive from the vehicle center-of-gravity point, and the correction is performed by adding the distance Lβ between the intersection and the center of gravity to the distance L. Is calculated from the angle θ, the distance L, and the distance Lβ between the intersection and the center of gravity using the equation ρ
3. The curve curvature estimating device according to claim 2, wherein the curve curvature estimating device is configured to be determined by: sin θ / L + Lβ.